If you want to replace that toilet, then check Terry's toilet discussion link. You say the mechanical parts have had it. No doubt, but they are easy to replace. There are kits that have the big rubber washer to seal the tank from the stool, new tank bolts and all of the other parts needed. Unless it's broken, the tank isn't worn out, just the parts. So, unless you really want to make a change, repair the old one, and it'll be ready for another 45 years use.